In need of help to create a transperant navigation bar for mobile view

Site URL: https://vuvuzela-lilac-s52g.squarespace.com/config/design/custom-css

I'm really eager to create a transparent navigation bar for mobil view. The navigation bar is transparent on website view, but I can't figure out how to create the same look for mobile view. 

I've been looking through multiple previous and similar posts in here, but nothing have been working for me so far. 

Can anybody help me with a CSS code in order to create a transparent navigation bar for mobile view, so it matches the navigation bar on website view?

website url: https://vuvuzela-lilac-s52g.squarespace.com/config/design/custom-css

Kindest,

Your site is private. Can you setup password & share url again?

My apologies tuanpan. Find below password and url:

url: https://vuvuzela-lilac-s52g.squarespace.com/config/settings/site-visibility
password: 123456

Thank you tuanphan. Works perfectly.